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SubjectRe: sched domains bringup race?
Keshavamurthy Anil S wrote:
> On Thu, Jul 15, 2004 at 07:13:46PM -0700, Dave Hansen wrote:
>
>>I keep getting oopses for the non-boot CPU in find_busiest_group().
>>This occurs the first time that the CPU goes idle. Those groups are set
>>up in sched_init_smp(), which is called after smp_init():
>>
>>static int init(void * unused)
>>{
>> ...
>> fixup_cpu_present_map();
>> smp_init();
>> sched_init_smp();
>>
>>But, the idle threads for the secondary CPUs are initialized in
>>smp_init(). So, what happens when a CPU tries to schedule (using sched
>>domains) before sched_init_smp() completes? I think it goes boom! :)
>>
>>Anyway, I was thinking that we should just hold the runqueue lock on the
>>non-boot CPUs until the sched domain init code is done. Does that sound
>>feasible?
>
>
> Even on my system which is Intel 865 chipset (P4 with HT enabled system)
> I see a bug check somewhere in the schedular_tick during boot.
> However if I move the sched_init_smp() after do_basic_setup() the
> kernel boots without any problem. Any clue here?
>
> static int init(void * unused)
> {
> ...
> fixup_cpu_present_map();
> smp_init();
> populate_rootfs();
> do_basic_setup();
>
> sched_init_smp();

There shouldn't be any problem doing that if we have to, obviously we
need to know why. Is it possible that cpu_sibling_map, or one of the
CPU masks isn't set up correctly at the time of the call?
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